Portable bladder ultrasound device provides accurate measurements in toddlers

The children’s module of the Bladder Scanner (BS), a portable ultrasound device used to measure bladder volume, shows acceptable accuracy in children 4 years of age and above, according to a recent study. However, device performance appears unreliable in younger children.

“The current comprehensive study to understand the role of BSs in the paediatric population revealed both limitations and possibilities for improvement. Applying BS may not produce an accurate measurement in those younger than 3 years old. This machine showed acceptable accuracy in all bladder filling ranges in those with more than 4 years,” the researchers said.

Twenty-nine paediatric patients (mean age 36.1 months, 51.7 percent boys) scheduled for preventive untethering for spinal dysraphism participated in the study. The BS device was used to measure bladder volume as children were undergoing cystometry. The difference between the BS-measured and cystometry-infused bladder volumes was expressed as a percentage of the age-adjusted estimated bladder capacity (%EBC).

The average EBC in the overall sample was 121 mL. At baseline, participants had a mean height and weight of 86.1 cm and 12.9 kg, respectively. None of the patients had known bladder abnormalities, history of bladder surgery, or continuous urine leakage due to incompetence of the bladder neck. Patient age ranged from 2–72 months. [J Pediatr Urol 2022;18:344-349]

Over the entire participant age range, a strong and significant correlation existed between the bladder volume as determined by cystometry infusion and by the BS scan (r, 0.95; p<0.001). The mean bias in measurement was 33 %EBC.

Of note, Bland-Altman plots showed that the BS device generally overestimated the actual bladder volume, with the mean bias being slightly higher than the acceptable limit.

Analysis according to patient age revealed that the BS device was much more accurate in older participants. The mean bias in those aged 4–6 years, for example, was only 22.8 %EBC, while such deviation from the cystometry-measured bladder volume was 47.5 %EBC in children ≤3 years of age.

At an assumed acceptable bias threshold of 30 %EBC, all measurements for the older age group would be deemed adequate, while none would be so for younger patients.

Repeated-measure analysis additionally showed that bias increased along with increasing infused volume.

“To the best of our knowledge, this is the first study to compare the measured volume with BS with actual (infused) volume during cystometry in children. The subgroup comparison by age and quartiles was also applied first. This was possible because the current study had a true comparison standard, and this revealed the measurement capability of this machine in a whole EBC range,” the researchers said.